The heat is on in West Antarctica

December 23rd, 2012 by eric

If it sounds like I don’t think Bromwich et al.’s results are anything new, let me correct that impression. The contribution of this new paper is huge. Bromwich et al. rely almost entirely on local data to produce the best-possible record of temperature from one location — Byrd Station in central West Antarctica. In contrast, our work relied heavily on interpolation of data from weather stations some distance from West Antarctica. Why didn’t we use the same data Bromwich et al. did? Well, we did, but the problem is that the Byrd Station record is actually several different records, taken at different times using different instruments. We felt that we could not splice these records together into one continous record, because instrument inter-calibration issues could easiily create spurious trends.

One of the chief contributions of the Bromwich team is that they carefully checked the calibration on the various temperature sensors and dataloggers that are used in the Byrd automatic weather station. It turns out that there were significant calibration issues and that correcting for them makes the temperature higher in the 1990s but somewhat lower in the 2000s (though still higher than in the 1960 – 1980s). That is a compelling finding, because it puts the weather station data in better agreement with the climate forecast reanalysis data explaining the cause of the winter warming trends (as described e.g. in Ding et al., 2011; 2012).

Another new aspect of the Bromwich et al. paper is that it shows that there is significant warming even in summer time in West Antarctica. This could arguably bode ill for the West Antarctic Ice Sheet, since if current trends continue it will mean more melting on the ice shelves there — ultimately leading to their collapse, as has already happened on the Antarctic Peninsula.

As Anais Orsi and I discuss in a News & Views article — not yet online, but evidently to be in the Februrary print issue of Nature Geoscience[Update, Steig and Orsi is now online here]– Bromwich et al.’s results are objectively the best record available of the last five decades of temperature change in West Antarctica. Note that the while the borehole data are the most important independent validation, they provide only a smoothed look at past temperatures; they do not resolve interannual or decadal variability. Bromwich et al.’s updated record for Byrd Station should now be routinely incorporated into global temperature compilations such as those done by GISS and CRU. Doing so will, I think, change the picture of climate change in the Southern Hemisphere, and not insignificantly.

There’s a lot more to be said — including some reasons why I don’t think the likelihood of surface-snow-melt-driven collapse of ice shelves is very high in West Antarctica — but I’m off to enjoy a respite from the internet for a few days. I’m going somewhere nice and cold and snowy.